Combined Sewer Overflow What is a CSO? A CSO is a Combined Sewer Overflow. In a combined sewer system, stormwater and sanitary sewage from domestic, commercial, and industrial sources flow together in a single pipe to the Water Reclamation Facility to be treated. During rainfall events, the pipes become full of stormwater and sewage. CSO outfalls allow excess flow to discharge to nearby water bodies, preventing backups at storm drains and in basements. The City of Akron currently has 34 CSO outfalls in the sewer collection system. • During wet weather, untreated wastewater discharges to the receiving streams along with large quantities of stormwater.• During wet weather the following types of contaminates may be present in the receiving waters: pathogens, bacteria, oxygen-demanding pollutants, suspended solids, nutrients, toxics and floatable matter. CSOs Outside of Akron Akron isn't the only city that is being required to upgrade its sewer system to meet EPA water quality standards. Akron is just one of 772 cities across the country with combined sewer overflows, according to the EPA. More information about CSOs across the State of Ohio can be found at the Ohio EPA's website. The EPA's Involvement The Federal Consent Decree requires the City of Akron to comply with the Clean Water Act of 1972 (CWA), and upgrade the sewer system so that the Ohio & Erie Canal, Cuyahoga River, Tuscarawas River and Little Cuyahoga River meet the established water quality standards. The City of Akron is seeking alternative methods to lower the overall cost of the program, including gray to green initiatives, as outlined in the Integrated Plan, which was submitted to the EPA in August of 2015. In December of 2015, the EPA approved three of the projects proposed in the Integrated Plan. The City of Akron continues to work with the EPA to explore opportunities to lower the cost of the program to help ease the burden on Akron residents.